JPH09166866A - Mark for aligning photomask and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to rapidly measure misalignment in a θ direction together with misregistration in X- and Y directions with high accuracy by composing the marks of X- and Y vernier calipers for measuring the alignment in the X- and Y directions and θ vernier calipers for measuring the alignment in the B direction inclined with both of X, Y. SOLUTION: The respective marks are composed of the X vernier calipers 1 arranged in the X direction, the Y vernier calipers 2 arranged in the Y direction orthogonal therewith and the θ1 vernier calipers 3 arranged in the 61 direction inclined at a prescribed angle with both of the X direction and Y direction. The marks 1A to 3A to be aligned which constitute the respective vernier calipers 1 to 3 are formed of plural pieces of graduations of a large width. On the other hand, the aligning marks 1B to 3B are formed of the graduations of the small width of the same number as the number of the marks 1A to 3A to be aligned. The measurement of the misalignment in the X- and Y directions and in the θ1 direction by the respective vernier calipers 1 to 3 is made possible by observing these marks with an optical microscope.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask alignment mark technique used in a photolithography technique, which is one of the manufacturing processes of semiconductor devices.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device, various individual elements such as a wiring layer, a contact hole, and an ion implantation region are formed on a wafer by using a mask, a photoresist, and a photolithography apparatus using a reduction projection exposure apparatus. The mask process is used. In such a manufacturing process, it is necessary to accurately align the pattern previously formed with the pattern to be formed later. Therefore, the alignment mark is formed on the wafer at the same time when the pattern is formed earlier. Every time (alignment mark), when forming the pattern later,
The previously formed alignment mark is detected, and alignment using the mark (alignment mark) of the pattern to be formed next is performed for this alignment mark to correct the misalignment with respect to the wafer. While doing the exposure.

However, even with the pattern formed in this way, in the shot projection exposure which is repeatedly performed, there is a certain probability that the pattern is not sufficiently aligned. If the degree of deviation exceeds the permissible range, the completed semiconductor chip will be a defective product due to, for example, an electrical short circuit between the wiring layer and the contact hole. Therefore, after the development, it is necessary to inspect the misalignment, and for the wafer in which an unacceptable misalignment is detected, the photoresist is removed and the photomask process is performed again, or it is necessary to extract and exhaust the wafer.

In order to easily carry out the inspection of the misalignment in such a photomask process by observing with an optical microscope, a technique using a caliper scale as an alignment mark has been proposed. This kind of caliper scale is, as shown in FIG. 4, a caliper scale in one direction on the wafer plane (X caliper scale, hereinafter X caliper) 11 and a scale in a direction orthogonal to it (Y caliper scale, hereinafter Y caliper). 12 and 12 are configured as one set. These X calipers 1
Of the 1 and Y calipers 12, 11A and 12A are calipers as alignment marks to be formed in the next step.
1B and 12B are calipers as the alignment marks formed in the previous process. The two calipers have slightly different pitches, and normally the pitch of the calipers to be aligned is configured to be slightly narrower than the pitch of the calipers to be aligned.

In the above-mentioned calipers to be aligned, the calipers to be aligned on the mask are transferred as a photoresist pattern on the wafer, and an etching process is performed using this photoresist, after which the photoresist is removed. Also, the calipers to be aligned are left on the wafer. Then, in the subsequent photomask process, the alignment caliper on the mask is transferred as a photoresist pattern on the wafer, and this becomes the alignment caliper, which is superposed on the caliper to be aligned and aligned.

Here, the figure shows a state in which there is no misalignment, and the center graduations of the alignment calipers 11B and 12B are located substantially in the center of the center graduations of the calipers 11A and 12A to be calibrated. It becomes a state. Further, when there is misalignment, the scales other than the center of the caliper to be aligned are positioned substantially at the center of the scales other than the center of the caliper to be aligned. Therefore, it is possible to measure the misalignment amount by considering which scale of the caliper to be aligned is located at the center of which scale of the caliper to be aligned and the pitch dimension of each caliper with an optical microscope. it can.

[0007]

In the conventional alignment using the X calipers and the Y calipers, it is possible to perform the alignment in each of the X direction and the Y direction, but it is possible to perform the alignment in both the X direction and the Y direction. There is a problem in that it is difficult to perform the alignment in a direction inclined at a predetermined angle, which is referred to as the θ direction here, by using an optical microscope and measure the deviation amount with high accuracy. For example, FIG. 5A is an example of a semiconductor static memory circuit in which the misalignment in the θ direction is strictly required, and includes a word line WL, a contact hole CH for extracting a bit signal, and a gate electrode of a drive transistor. G
Are arranged in the diagonal direction at intervals of d11, d12 and d13, respectively, and d11 and d12 are designed to have the same length. Here, these word lines WL, gate electrodes G,
Since the contact hole CH is formed by a photomask process different from that of the contact hole CH, if misalignment in the θ direction occurs, an error occurs in these intervals, and if the amount of misalignment increases, they are short-circuited with each other and become defective. Similarly, FIG. 5B shows a power supply line BL of the semiconductor static memory circuit,
In the example of the contact holes CH1 and CH2 of the storage node, the gaps d21 and d2 are caused by misalignment in the θ direction.
If there is a shift in 2, a short circuit may occur between them.

It is not impossible to measure such misalignment in the θ direction using the X calipers and the Y calipers shown in FIG. For example, when measuring the misalignment in the 45 ° direction with respect to the X direction and the Y direction, the misregistration amount in each of the X direction and the Y direction, and 0.1 μ for each
If there is a misalignment of m, the misalignment amount at an angle of 45 ° is 0.1 μm × √2≈0.14 μm. With respect to the deviation amount in the θ direction other than the oblique 45 °, the absolute value of the deviation amount can be measured by squaring the measured deviation amounts in the X direction and the Y direction and calculating the square root of the sum based on the same principle.

However, in this method, the X direction and the Y direction are
Since it is necessary to measure the misalignment amount in each direction and to perform the above-mentioned calculation using these, the misalignment inspection time is increased, which is inconvenient for mass production of semiconductor devices. For example, in the above-mentioned example, the limit of misalignment is ± 0.1 μm, and the control limits of the X caliper and the Y caliper are ± 0.
When 1 μm is set, the misalignment amount is determined individually by using the misalignment amounts in the X direction and the Y direction, and the misalignment in the θ (45 °) direction is 0.14 μm.
Even if the thickness does not fall within 0.1 μm, it cannot be immediately judged by visual observation with a microscope, the calculation must be waited, and the inspection time becomes long.

Japanese Patent Laid-Open No. 1-193743 discloses a technique for measuring misalignment in directions other than the X and Y directions. This is a dedicated pattern for inspecting rotational misalignment in shot units. Is provided,
The dedicated pattern is arranged on the outer peripheral portion of the reticle, and the rotation deviation is inspected by the degree of overlap with the adjacent shot. Therefore, the problem of misalignment in the θ direction as described above cannot be solved.

An object of the present invention is to provide a photomask alignment mark and this alignment mark capable of measuring the positional deviation in the θ direction together with the misalignment in the X and Y directions with high accuracy and speed. It is to provide a semiconductor device having the following.

[0012]

Means for Solving the Problems An alignment mark according to the present invention comprises a first alignment mark formed on one photomask and a second alignment mark formed on another photomask aligned with the first alignment mark. The alignment marks are the X calipers that measure the alignment in the X direction, the Y calipers that measure the alignment in the Y direction, and the alignment in the θ direction that is inclined with respect to both the X and Y directions. It is characterized in that it is composed of θ calipers.

For example, the X caliper is composed of a plurality of scales arranged in the X direction, the Y caliper is composed of a plurality of scales arranged in the Y direction, and the θ caliper is a plurality of scales arranged in the θ direction. It is composed of scales. The θ caliper may be composed of a plurality of scales arranged in the X direction or the Y direction. Furthermore, the θ caliper may be composed of a plurality of θ calipers for measuring the alignment in the θ direction with different inclination angles.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a pattern configuration diagram of an alignment mark and an alignment mark according to the first embodiment of the present invention. Each mark is an X caliper 1 arranged in the X direction.
And Y calipers 2 arranged in the Y direction orthogonal to this,
Predetermined angle in both X and Y directions, here 45
It is composed of θ1 calipers 3 arranged in the θ1 direction inclined at an angle of °. The alignment marks 1A, 1B, 1C forming each of the calipers 1 to 3 are formed of a plurality of wide-width graduations, and each graduation is formed at a predetermined pitch interval. On the other hand, the alignment marks 1B, 2B, 3B that form the calipers 1, 2, 3 are the alignment marks 1A, 2
The graduations are formed in the same number as A and 3A, and each graduation is formed at a pitch interval slightly smaller than the graduation of the alignment mark. For example, the alignment marks 1A, 2
A, 3A pitch interval is 1 μm, and alignment mark 1
The pitch intervals of B, 2B and 3B are set to 0.95 μm.

The alignment marks and the alignment marks as described above are the same as the conventional ones.
A and 3A are formed on the wafer in the previous photomask process,
The alignment marks 1B, 2B, 3B are formed on the wafer in a photomask process which will be performed later. Then, by observing these marks with an optical microscope, alignment can be performed. For example, in the figure, the alignment marks 1B, 2B, 3
The scale at the center of B is the alignment marks 1A, 2A, 3A
It is located at the center of the graduation in the center of, and in this state, there is no misalignment between the marks.

On the other hand, although not shown, when the scales other than the center of the alignment marks 1B, 2B, 3B are located at the center of the scales other than the center of the alignment marks 1A, 2A, 3A, There is a misalignment between the marks. This misalignment amount is the difference between the pitch dimensions of both marks, that is, 1-0.95 =
It can be measured in units of 0.05 μm. Therefore, when observing both marks, it is confirmed at what number scale from the center scale of each mark the centers of both marks are overlapped, and the number of the scale and the measurement unit of 0.05 μm. Therefore, the amount of deviation can be measured. In this embodiment, each mark is 7
Since it is composed of individual scales, misalignment in the range of ± 0.15 μm can be measured.

Therefore, in the present embodiment, the X caliper 1 can measure the misalignment of both marks in the X direction, the Y caliper 2 can measure the misalignment in the Y direction, and the θ1 caliper 3 can measure the misalignment in the θ1 direction. Deviation can be measured. In each direction, since the above-mentioned deviation in 0.05 μm units can be measured by each caliper, the misalignment between both marks, that is, the respective patterns of the preceding photomask and the following photomask, can be measured in the X direction and the Y direction.
Direction and the θ1 direction, respectively. As a result, highly accurate alignment can be realized even in the manufacture of a semiconductor device in which alignment precision is strictly required in the θ1 direction. Therefore, the margin of the pattern design in the θ direction can be reduced, which is advantageous in achieving high integration of the semiconductor device. Further, since the alignment in the θ1 direction can be confirmed at a glance by observing with an optical microscope, rapid alignment can be performed.

FIG. 2 is a diagram showing a second embodiment of the present invention, in which parts equivalent to those in FIG. 1 are designated by the same reference numerals. This embodiment is an example in which the θ2 caliper 4 composed of the alignment mark 4A and the alignment mark 4B is arranged along the θ2 direction that is the same in the Y direction and is opposite to the X direction, Other than this θ2 direction is different from the θ1 direction in FIG. 1, the other configurations are the same, and as in the embodiment of FIG. 1, misalignment in the θ2 direction can be quickly measured in a fine measurement unit, and the speed can be increased. It is possible to make precise alignment.

FIG. 3 is a diagram showing a third embodiment of the present invention, in which X1 calipers 1 and Y calipers 2 as well as θ1 calipers 3 and θ2 calipers 4 are arranged together, and they are orthogonal to each other.
The configuration is such that the alignment in one direction and the θ2 direction can be performed at the same time. In this embodiment, θ1
The scales of calipers 3 and θ2 calipers 4 are shown in Fig. 1, respectively.
By moving the scales of each caliper shown in FIG. 2 in parallel in the Y direction, the calipers are arranged in the X direction with a predetermined pitch interval in the θ1 direction and the θ2 direction. And the misalignment in the θ1 direction and the θ2 direction can be measured in the same manner. Therefore, each misalignment in the X direction, Y direction, θ1 direction, and θ2 direction can be measured quickly and with high accuracy. Also, in this way, each scale of θ1 caliper and θ2 caliper is X
By arranging them in the directions, the lengths of the θ1 and θ2 calipers in the Y direction can be shortened, the area occupied by the entire alignment mark can be minimized, and high integration of the semiconductor device can be achieved. Further, since the θ1 calipers and the θ2 calipers are arranged side by side, the misalignment in the θ1 direction and the θ2 direction can be observed in contrast, and the observation work efficiency can be improved.

Here, in each of the above embodiments, the θ1 direction, θ
Although the two directions show an example in which the two directions are inclined at 45 ° in the X direction and the Y direction, the present invention is also applicable to the case of being inclined at other angles, for example, 30 ° and 60 ° with respect to the X direction. Applicable to Further, the scales of the θ calipers can be arranged side by side in the Y direction. In some cases, the X calipers may be arranged side by side in the Y direction and the Y calipers may be arranged side by side in the X direction. Can be changed. Further, it goes without saying that the pitch and the number of scales of each caliper are not limited to the values in the above embodiment.

[0021]

As described above, the alignment mark of the present invention can be applied to both the X caliper for measuring the alignment in the X direction, the Y caliper for measuring the alignment in the Y direction, and the X caliper for both the X direction and the Y direction. Θ to measure the alignment in the θ direction inclined to
Since it is composed of calipers, it is of course possible to easily measure misalignment in the X and Y directions by observing it with an optical microscope, etc. Can be measured quickly and with high accuracy. As a result, it is possible to measure the misalignment in the semiconductor device, which requires strict alignment accuracy in the θ direction with high accuracy, reduce the design margin in the θ direction, and achieve high integration of the semiconductor device.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an alignment mark according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an alignment mark according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an alignment mark according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional alignment mark.

FIG. 5 is a diagram showing an example of a pattern of a conventional semiconductor device that requires alignment accuracy in the θ direction.

[Explanation of symbols]

 1 X caliper 2 Y caliper 3 θ1 caliper 4 θ2 caliper 1A, 2A, 3A, 4A Alignment mark 1B, 2B, 3B, 4B Alignment mark

Claims (7)

[Claims] 1. A first alignment mark formed on one photomask and a second alignment mark formed on another photomask are relatively compared to align the two photomasks. In the alignment mark, the first alignment mark and the second alignment mark are each X.
It is composed of an X caliper that measures the alignment in the direction, a Y caliper that measures the alignment in the Y direction, and a θ caliper that measures the alignment in the θ direction that is inclined with respect to both the X direction and the Y direction. The alignment mark on the photomask. 2. The X caliper is composed of a plurality of scales arranged in the X direction, the Y caliper is composed of a plurality of scales arranged in the Y direction, and the θ caliper is a plurality of scales arranged in the θ direction. The alignment mark of the photomask according to claim 1, wherein the alignment mark comprises a scale. 3. The alignment mark of the photomask according to claim 1, wherein the θ caliper is composed of a plurality of scales arranged in the X direction or the Y direction. 4. The θ calipers are θ of different inclination angles.
The alignment mark of the photomask according to any one of claims 1 to 3, which is composed of a plurality of calipers for measuring the alignment of directions. 5. The first alignment mark and the second alignment mark are different in the width dimension of the scale, and the overlapping positions of both marks are observable.
Alignment mark on one of the photo masks. 6. The first alignment mark is formed on a photomask used in a previous photomask process, and the second alignment mark is formed on a photomask used in a subsequent photomask process. Alignment mark on the photomask of any one of 1 to 5. 7. A semiconductor device provided with the alignment mark according to claim 1.